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The purpose of the study was to assess the influence of a preceding mountain ultramarathon on the impact between the foot and the ground and the resulting soft tissue vibrations (STV). Two sessions of measurements were performed on 52 trail runners, before and just after mountain trail running races of various distances (from 40 to 171 km). Triaxial accelerometers were used to quantify the foot-ground impact (FGI) and STV of both

Cyclists are exposed for a long period to continuous vibrations. When a muscle is exposed to vibration, its efficiency decreases, the onset of fatigue occurs sooner, and the comfort of the cyclist is reduced. This study characterised the

Hintzy, F, Gregoire, N, Samozino, P, Chiementin, X, Bertucci, W, and Rossi, J. Effect of thigh-compression shorts on muscle activity and soft-tissue vibration during cycling. J Strength Cond Res 33(8): 2145-2152, 2019-This study examined the effects of different levels of thigh compression (0, 2, 6, and 15 mm Hg) in shorts on both vibration and muscle activity of the thigh during cycling with superimposed vibrations. Twelve healthy males performed a 18-minute rectangular cycling test per shorts condition (randomized cross-over design) on a specifically designed vibrating cycloergometer. Each test was composed of 2 intensity levels (moderate then high) and 3 vibration frequencies of 18.3, 22.4, and 26.3 Hz, corresponding to cadences of 70, 85, and 100 rpm, respectively. Muscle vibrations were measured with 2 triaxial accelerometers located before and on the lower-body compression garment, to quantify, respectively, the input and output vibrations, and vastus lateralis muscle activity was measured using surface electromyography. Both vibration and electromyography signals were measured throughout the tests and quantified using root-mean-square analyses. The study showed that the use of a thigh-compression shorts at 6-15 mm Hg significantly reduced both the vibration transmissibility to the thigh and the muscle activity, with higher effect size at higher superimposed vibrations. The thigh-compression shorts garment therefore seems to be 1 way to dampen vibrations transmitted to the cyclists and then to reduce the negative consequences of these vibrations on muscles.

Non-circular chainrings have been reported to alter the crank angular velocity profile over a pedal revolution so that more time is spent in the effective power phase. The purpose of this study was to determine whether sprint cycling performance could be improved using a non-circular chainring (Osymetric: ellipticity 1.25 and crank lever mounted nearly perpendicular to the major axis), in comparison with a circular chainring. Twenty sprint cyclists performed an 8 s sprint on a cycle ergometer against a 0.5 N/kg-1 friction force in four crossing conditions (non-circular or circular chainring with or without clipless pedal). Instantaneous force, velocity and power were continuously measured during each sprint. Three main characteristic pedal downstrokes were selected: maximal force (in the beginning of the sprint), maximal power (towards the middle), and maximal velocity (at the end of the sprint). Both average and instantaneous force, velocity and power were calculated during the three selected pedal downstrokes. The important finding of this study was that the maximal power output was significantly higher (+ 4.3%, p < 0.05) when using the non-circular chainring independent from the shoe-pedal linkage condition. This improvement is mainly explained by a significantly higher instantaneous external force that occurs during the downstroke. Non-circular chainring can have potential benefits on sprint cycling performance.

The aim of this study was to investigate the effect of using poles on foot-ground interaction during trail running with slopes of varying incline. Ten runners ran on a loop track representative of a trail running field situation with uphill (+9°), level and downhill (-6°) sections at fixed speed (3.2 m.s(-1)). Experimental conditions included running with (WP) and without (NP) the use of poles for each of the three slopes. Several quantitative and temporal foot-ground interaction parameters were calculated from plantar pressure data measured with a portable device. Using poles induced a decrease in plantar pressure intensity even when the running velocity stayed constant. However, the localisation and the magnitude of this decrease depended on the slope situations. During WP level running, regional analysis of the foot highlighted a decrease of the force time integral (FTI) for absolute (FTIabs; -12.6%; P

Resume Objectifs Quantifier le debit energetique net total et la contribution des voies aerobie et anaerobie lactique lors d’un slalom geant (SG) realise sur le terrain chez l’enfant skieur competiteur. Methodes Sept skieurs evoluant en categorie minime (14,0 ± 0,5 ans) ont participe a l’etude. Une evaluation de la consommation pic d’oxygene a d’abord ete obtenue lors d’un effort incremental standardise. Un enregistrement continu de la consommation d’oxygene associe a des microprelevements sanguins arterialises ont ensuite ete realises lors d’un SG pour quantifier le debit energetique total et l’implication des voies anaerobie lactique et aerobie. Resultats A la fin du SG, qui durait 76,4 ± 10,9 secondes, la consommation d’oxygene etait de 64,0 ± 7,8 % de la consommation pic d’oxygene et la concentration sanguine en lactate de 5,7 ± 2,2 mmol/L. Le debit energetique total lors du SG etait de 31,7 ± 6,7 kJ/min. La participation relative des voies aerobie et anaerobie lactique etait de 69,7 ± 16,7 % et 30,3 ± 16,7 %, respectivement. Conclusion Le debit energetique total du skieur minime est faible lors d’un SG, notamment par rapport a celui de l’adulte, et l’aptitude a l’augmenter semble influencee par l’activite de la voie anaerobie lactique.

External ankle supports, such as ankle braces, may improve postural stability by stimulating cutaneous receptors. It remains unknown whether these supports have an effect on the posture central regulation. The aim of this study was to determine the effect of wearing a soft ankle brace on soleus H-reflex amplitude and presynaptic inhibition during standing. Sixteen subjects stood on a rigid floor with their eyes opened, either barefoot or wearing a soft ankle brace. H-reflex amplitude was measured on the soleus muscle by stimulating the tibial nerve electrically. Modulation of presynaptic inhibition was assessed by conditioning the H-reflex with fibular nerve (D1 inhibition) and femoral nerve (heteronymous facilitation) electrical stimulations. The unconditioned H-reflex amplitude was significantly greater when wearing the ankle brace than barefoot, whereas D1 and HF conditioned soleus H-reflex did not differ significantly between bracing conditions. These results suggest that the ankle brace increased the soleus motoneuron excitability without altering presynaptic mechanisms, potentially because of increased cutaneous mechanoreceptors afferent signals provided by the soft ankle brace.

A theoretical integrative approach is proposed to understand the overall mechanical characteristics of lower extremities determining jumping ability. This approach considers that external force production during push-off is limited by mechanical constraints imposed by both movement dynamics and force generator properties, i.e. lower extremities characteristics. While the velocity of the body depends on the amount of external force produced over the push-off, the capabilities of force production decrease with increasing movement velocity, notably for force generators driven by muscular contraction, such as lower extremities of large animals during jumping from a resting position. Considering the circular interaction between these two mechanical constraints, and using simple mathematical and physical principles, the proposed approach leads to a mathematical expression of the maximal jump height an individual can reach as a function of only three integrative mechanical characteristics of his lower extremities: the maximal force they can produce ( F ¯ 0 ), the maximal velocity at which they can extend under muscles action ( v ¯ 0 ) and the distance of force production determined by their usual extension range ( h PO ). These three integrative variables positively influence maximal jump height. For instance in humans, a 10% variation in F ¯ 0 , v ¯ 0 or h PO induces a change in jump height of about 10–15%, 6–11% and 4–8%, respectively. The proposed theoretical approach allowed to isolate the basic mechanical entities through which all physiological and morphological specificities influence jumping performance, and may be used to separate the very first macroscopic effects of these three mechanical characteristics on jumping performance variability.

Resume Objectif Il s’agissait d’analyser les modifications perceptives, musculaires et physiologiques induites par l’utilisation d’une selle ergonomique sans appui perineal et permettant les pivotements mediolateraux du bassin. Methode Huit sujets non cyclistes ont realise un exercice sur cycloergometre constitue de quatre paliers de trois minutes chacun a puissance croissante (50 to 200 W), avec des selles ergonomique et classique, l’ordre des selles etant randomise. La perception subjective de l’effort, l’activite electromyographique (EMG) de six muscles du membre inferieur et le rendement mecanique ont ete mesures a chaque palier. Conclusions Le rendement a 50 W etait significativement degrade avec la selle ergonomique versus classique, ce qui laisse supposer un travail interne augmente cause par la mobilite du bassin avec cette selle. En revanche, a puissance elevee, il n’existe plus de difference de rendement entre les deux selles et la perception de l’effort est significativement moindre avec la selle ergonomique. Des moindres activations musculaires (−18 et −23 %) se produisent a 200 W sur les muscles vaste lateral (VL) (un des principaux producteurs de force musculaire) et tibialis anterieur (un des muscles facilitant le passage des points morts), ce qui plaide en faveur d’une amelioration de l’efficacite de pedalage avec la selle ergonomique.

Our aim was to clarify the relationship between power output and the different mechanical parameters influencing it during squat jumps, and to further use this relationship in a new computation method to evaluate power output in field conditions. Based on fundamental laws of mechanics, computations were developed to express force, velocity and power generated during one squat jump. This computation method was validated on eleven physically active men performing two maximal squat jumps. During each trial, mean force, velocity and power were calculated during push-off from both force plate measurements and the proposed computations. Differences between the two methods were not significant and lower than 3% for force, velocity and power. The validity of the computation method was also highlighted by Bland and Altman analyses and linear regressions close to the identity line (P

Purpose The purpose of this study was to examine the relationships of VO2 during unloaded arm cranking and leg cycling exercises to respectively relevant upper and lower limbs anthropometrical characteristics. Method Fifteen males completed a 5-min unloaded bout on an arm crank ergometer (60 rpm) and a cycle ergometer (90 rpm). VO2 corresponding to each unloaded exercise (VO2unload), body mass, lengths, and circumferences of upper and lower limbs were measured. Results Upper limbs cranking showed a significantly lower (P

The aim of this study was to describe elliptical cycle locomotion by muscular, kinematics, physiological and perceptual parameters during submaximal and maximal exercises. Seven men performed an incremental test until exhaustion. Pulse rate, ratings of perceived exertion (6-20 Borg's scale), muscular activity of 8 muscles (higher and lower limbs muscles) and elbow, shoulder, hip and knee joint amplitudes were continuously recorded. Pulse rate reached about 70% of the theoretical maximal pulse rate after 3 minutes of submaximal exercise and about 95% at the end of the maximal exercise; the sensation of this effort being respectively described as "weak" and "very hard". EMG analysis indicated that all investigated muscles were activated, especially knee and hip extensor muscles. Kinematic analysis showed that all joints were activated especially the elbow, shoulder and knee. The elliptical cycle locomotion led to global body activation (both higher and lower limbs activity) and therefore induced a relatively significant cardiac activation even at low intensity. We therefore suggest that elliptical cycle locomotion is a unique pattern.

This study analysed muscular, mechanical and physiological parameters using a circular chainring (CC) and a non circular Osymetric chainring (OC). OC was characterized by the use of 11 lowerradius during top and bottom dead cerner and a higher radius during downstroke and upstroke phases. Twelve triathleres performed (i) an 8 min submaximal test and (ii) Iwo 8 s maximal sprint rests. Gross efficiency was calculated during the submaximal rest. InSlantaneous external force and pedalling rate 'vere recorded and the instantaneous nel crank torque was calculated during both tests. Lower limb muscles coordination pattern (timing and magnirude) were also recorded. During the submaximal rest, the only significant differences were the lower net crank torque or OC vs. CC at (f and I gOa and the higher nel crank torque of OC vs. CC at 90° (P < 0.(5). Concerning the sprint test, the only significant difference was the higher burst duration of the biceps femoris muscle with OC (P < 0.05). Present results indicate that OC facilitated mechanically the foot path at 0° and 1800 Nevertheless. this mechanical effect did nOI seem to be sufficient to improve performance since the muscles coordination pattern was not modified.

Purpose: The objective of this study was to partly explain, from electromyographical (EMG) activity, the decrease in power output beyond optimal pedaling rate (PRopt) during sprint cycling. Methods: Eleven cyclists performed four 8-s nonisokinetic sprints on a cycle ergometer against four randomized friction loads (0.5, twice 0.75, and 0.9 N·kg-1 of body mass). Power output and EMG activity of both right and left gluteus maximus, rectus femoris, biceps femoris, and vastus lateralis were measured continuously. Individual crank cycles were analyzed. Crank angles corresponding to the beginning and the peak of each downstroke and EMG burst onset and offset crank angles were computed. Moreover, crank angles corresponding to the beginning and the end of muscle force response were determined assuming a 100-ms lag time between the EMG activity and the relevant force response (or electromechanical delay). Results: Muscle coordination (EMG onset and offset) was altered at high pedaling rates. Thus, crank angles corresponding to muscle force response increased significantly with pedaling rate. Consequently, at pedaling rates higher than the optimal pedaling rate, force production of lower-limb extensor muscles was shifted later in the crank cycle. Mechanical data confirmed that downstrokes occurred later in the crank cycle when pedaling rate increased. Hence, force was produced on the pedals during less effective crank cycle sectors of the downstroke and during the beginning of the upstroke. Conclusion: During nonisokinetic sprint cycling, the decrease in power output when pedaling rates increased beyond PRopt may be partly explained by suboptimal muscle coordination.

Non-circular chainrings alter the crank velocity profile over a pedalling cycle. The aim of this study was to investigate the effect of this altered crank velocity profile on the aerobic performance compared to a circular chainring (CC). Ten male non-cyclists performed two incremental maximal tests at 80 rpm on a cycle ergometer: one with a circular (Shimano) and the other with a non-circular chainring Osymetric® (Somovedi), at least 50 h apart. Each test started with a workload of 100 W lasting 3 min. During the first 12 min, the workload was increased by 30 W every 3 min. Thereafter, the workload was increased by 30 W every 2 min until exhaustion. The power output, the intra-cycle crank angular velocity and the physiological parameters were monitored continuously, averaged over the last 30 s of each increment and at exhaustion, and compared for the two chainrings. Results showed a higher maximal aerobic power attained with the non-circular chainring (362.6 ± 37.9 vs. 338.8 ± 32.6 W, p

Objective. The purpose of this study was to compare four methods of calculating the mechanical efficiency of hand–rim wheelchair propulsion. Methods. After completing a maximal incremental test, 18 untrained able-bodied males (mean age 22 years) performed four 4-min bouts of exercise (0%, 40%, 55%, and 70% of peak power output) on a wheelchair–ergometer. The mechanical efficiency was calculated during each submaximal bout by the ratio of work accomplished to the amount of energy expended with four indices: gross (no base-line correction), net (resting metabolism as base-line correction), work (unloaded movement as base-line correction) and delta (measurable work as base-line correction) indices. Results. Work efficiency (16.8–13.8%) were significantly higher (P

The aim of this study was to determine the relationship between force and velocity parameters during a specific multi-articular upper limb movement--namely, hand rim propulsion on a wheelchair ergometer. Seventeen healthy able-bodied females performed nine maximal sprints of 8 s duration with friction torques varying from 0 to 4 N x m. The wheelchair ergometer system allows measurement of forces exerted on the wheels and linear velocity of the wheel at 100 Hz. These data were averaged for the duration of each arm cycle. Peak force and the corresponding maximal velocity were determined during three consecutive arm cycles for each sprint condition. Individual force-velocity relationships were established for peak force and velocity using data for the nine sprints. In line with the results of previous studies on leg cycling or arm cranking, the force-velocity relationship was linear in all participants (r = -0.798 to -0.983, P0.01). The maximal power output (mean 1.28 W x kg(-1)) and the corresponding optimal velocity (1.49 m x s(-1)) and optimal force (52.3 N) calculated from the individual force-velocity regression were comparable with values reported in the literature during 20 or 30 s wheelchair sprints, but lower than those obtained during maximal arm cranking. A positive linear relationship (r = 0.678, P0.01) was found between maximal power and optimal velocity. Our findings suggest that although absolute values of force, velocity and power depend on the type of movement, the force-velocity relationship obtained in multi-articular limb action is similar to that obtained in wheelchair locomotion, cycling and arm cranking.

To determine the optimal pedalling rate that minimises both the oxygen consumption (fV(O2,min)) and the energy cost of cycling (f(Cr,min)), 22 male subjects were asked to cycle on an ergometer on five occasions of 4 min each at a constant power output of 150 W and at pedalling rates of 40, 60, 80, 100 and 120 rpm. The oxygen consumption (V(O2) in millilitres per minute per kilogram) and the energy cost (Cr in joules per kilogram per metre) were determined during each period. The individual V(O2)-pedalling rate and Cr-pedalling rate relationships were fitted by parabolic regressions which allowed the determination for each individual of fV(O2,min) [mean (SD) 57.0 (4.9) rpm] and f(Cr,min) [101.1 (3.2) rpm], respectively. Contrary to the values obtained for fV(O2,min), those for f(Cr,min) were in agreement with the pedalling rates (90-110 rpm) usually selected in road cycling. It is therefore suggested that the minimisation of Cr is the main factor that determines the pedalling rate in field conditions. The lack of a significant correlation between fV(O2,min) and f(Cr,min) further indicated that, although fV(O2,min) is often used for determining the metabolic capacities of subjects, f(Cr,min) is a better index of optimal mechanical parameters of cycling in field conditions.

Resume Objectifs – Le but de cette experimentation etait d'etudier les relations entre les variables mecaniques de force, vitesse et puissance maximales developpees lors de sprints courts sur bicyclette ergometrique et les performances chronometriques lors de departs en starting-blocks en sprint en course a pied chez des sujets sprinters masculins entraines. Methodes – Sept sprinters espoir de niveau interregional ont realise dans un ordre aleatoire trois sprints de 6 s sur bicyclette ergometrique contre des forces de friction de 0,4, 0,6 et 0,8 N.kg −1 ainsi que trois departs en starting-blocks sur 30 m. Les valeurs maximales de force, de vitesse et de puissance developpees sur bicyclette ergometrique et les temps a 5, 10 et 30 m en sprint ont ete mesures. Resultats – Les vitesses moyennes entre 5 et 10 m et a 10 m sont significativement proportionnelles a la puissance maximale relative a la masse corporelle (r = 0,931 ; p p Conclusion – La puissance maximale relative a la masse corporelle (i.e., l'explosivite) des membres inferieurs mesuree lors de sprints sur bicyclette ergometrique semble etre un facteur determinant lors du debut de la mise en action en sprint (entre 5 et 10 m) chez ces athletes.

Resume Objectifs. Le but de cette etude etait de comparer les caracteristiques mecaniques d'un sprint mesurees sur cycloergometre non isocinetique avec deux types de pedales (automatiques ou sans maintien avec la chaussure). Methodes. Deux groupes de cyclistes (internationaux—nationaux et regionaux) ont realise quatre sprints de 8 secondes contre deux charges de friction (0,5 et 1,1 N.kg−1). Une analyse de la variance a deux facteurs (pedales et groupe) a ete realisee. Resultats. Les valeurs moyennes par coup de pedale de force, vitesse et puissance maximales relevees avec les pedales automatiques etaient significativement superieures a celles sans pedales non automatiques, quelle que soit la charge de friction. Conclusions. Cette amelioration de la puissance maximale a pu etre expliquee par une augmentation des valeurs optimales de vitesse ou de force, lorsque la charge de friction etait elevee ou faible. II semblerait que l'amelioration de la performance lors de l'utilisation de pedales automatiques puisse etre expliquee par l'augmentation de l'activation musculaire et/ou par une coordination intermusculaire amelioree.

The aim of this study was to compare optimal pedalling velocities during maximal (OVM) and submaximal (OVSM) cycling in human, subjects with different training backgrounds. A group of 22 subjects [6 explosive (EX), 6 endurance (EN) and 10 non-specialised subjects] sprint cycled on a friction-loaded ergometer four maximal sprints lasting 6 s each followed by five 3-min periods of steady-state cycling at 150 W with pedalling frequencies varying from 40 to 120 rpm. The OVM and OVSM were defined as the velocities corresponding to the maximal power production and the lowest oxygen consumption, respectively. A significant linear relationship (r2 = 0.52, P < 0.001) was found between individual OVM [mean 123.1 (SD 11.2) rpm] and OVSM [mean 57.0 (SD 4.9) rpm, P < 0.001] values, suggesting that the same functional properties of leg extensor muscles influence both OVM and OVSM. Since EX was greater than EN in both OVM and OVSM (134.3 compared to 110.9 rpm and 60.8 compared to 54.0 rpm, P < 0.01 and P < 0.05, respectively) it could be hypothesised that the distribution of muscle fibre type plays an important role in optimising both maximal and submaximal cycling performance.

Resume Introduction. – Le but de cette etude etait d'analyser l'evolution de la fatigue neuromusculaire des muscles vastus lateralis et gastrocnemius medialis au cours d'un test temps limite de pedalage a 100 % de puissance maximale aerobie. Synthese des faits. – L'amplitude de l'EMG augmentait des le debut du test puis diminuait apres l'atteinte de la valeur maximale, chez tous les sujets et pour les deux muscles, alors que la duree des bouffees d'EMG ne variait pas. Conclusion. – La diminution de l'amplitude de l'EMG vers la fin du test alors que l'intensite restait constante semble traduire la mise en jeu de muscles synergistes, ce qui temoigne des mecanismes adaptatifs sous-jacents au processus de fatigue.

The purpose of the present experiment was to investigate the immediate effects of a cycling exercise on postural control during quiet standing in healthy young adults. To this aim, 12 university students were asked to stand upright as immobile as possible, with their eyes closed, prior to and following a 15 min cycling exercise performed at a power output of 200 W. Centre of foot pressure (CP) displacements, recorded using a force platform along both the medio-lateral (ML) or antero-posterior (AP) axes, were used to compute the motions of the vertical projection of the centre of gravity (CG(v)) and those of the difference between the CP and the CG(v) (CP - CG(v)). Metabolic (heart rate, respiratory exchange ratio and blood lactate concentration) and psychological (rate of perceived exertion) measurements ensured that subjects were fatigued at the end of the cycling exercise. The cycling exercise induced a decreased of both CG(v) and CP - CG(v) motions along the AP-axis, whereas no significant changes were observed along the ML-axis. These discrepancies of the postural effects according to the direction of balance are likely to stem from the directionally sensitive activity of postural muscles, when considering (1) what the cycling exercise involved in terms of joints and tendons receptors stimulation and lower limb muscles recruitment (i.e. sagittal plane movers of the lower extremities) and (2) the skeletal muscles involved in postural control during quiet standing (i.e. sagittal and frontal plane movers of the lower extremities for the AP and ML balance, respectively).

The aim of this study was to evaluate the stabilisation of the wrist joint and the ad hoc wrist muscles activations during the two principal phases of the freestyle stroke. Seven male international swimmers performed a maximal semi-tethered power test. A swimming ergometer fixed on the start area of the pool was used to collect maximal power. The electromyography signal (EMG) of the right flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) was recorded with surface electrodes and processed using the integrated EMG (IEMG). Frontal and sagittal video views were digitised frame by frame to determine the wrist angle in the sagittal plane and the principal phases of the stroke (insweep, outsweep). Important stabilisation of the wrist and high antagonist muscle activity were observed during the insweep phase due to the great mechanical constraints. In outsweep, less stabilisation and lower antagonist activities were noted. Factors affecting coactivations in elementary movements, e.g. intensity and instability of the load, accuracy and economy of the movement were confirmed in complex aquatic movement.

The aim of this work was to analyse the effect of a non-circular chainring during sub and supra-maximal cycling conditions on physiological, mechanical and muscular data. Results showed that the use of the non-circular chainring was beneficial during top and bottom dead centres by decreasing the effective force for a same external force for sub-maximal condition and by increasing the crank angular velocity for supra-maximal condition. However, this non-circular chainring was without effect during the pedal downstroke.

This study proposed a non-invasive method to determine the gross (GE, no baseline correction), net (NE, resting metabolism as the baseline correction) and work (WE, unloaded cycling as the baseline correction) efficiencies during cycling at an intensity higher than the maximal aerobic power (MAP). Twelve male subjects performed two exercises consisting of 4 min at 50% MAP followed either by 8 min at 63% MAP or by 8 sequences of 60 s divided into 10 s at 130% MAP and 50 s at 50% MAP (i.e., 63% MAP on average). Oxygen uptake was continuously measured to calculate GE, NE and WE at 50%, 63% and 130% MAP, and the data presented as the means and standard deviations. The GE values were 18.2%, 19.1%, 22.7%, the NE values were 22.4%, 22.8%, 24.3% and the WE values were 34.2%, 31.4% and 27.2% at 50%, 63% and 130% MAP, respectively. The GE and NE increased (P

The effects of endurance training in normoxia or in hypoxia on time to exhaustion ( T(lim)) at the work rate corresponding to peak oxygen uptake (VO(2peak)) were examined at sea level in 13 healthy subjects. Before and after training the subjects performed the following: (1) incremental exercises up to exhaustion to determine peak oxygen uptake in normoxia (VO(2peak)N), the percentage of this value at the 4 mmol l(-1) blood lactate concentration (VO(2)4%N) and the work rate corresponding to VO(2peak)N (Pa(peak)N), (2) a 5-min 90% Pa(peak)N exercise followed by a 10-min passive recovery to determine the maximal blood lactate concentration (La(max)) measured during the recovery, and (3) a T(lim) at Pa(peak)N. Training consisted of pedalling 2 h a day, 6 days a week, for 4 weeks. Five subjects trained in normobaric hypoxia [HT; partial pressure of inhaled oxygen ( P(I)O(2)) 89 mmHg] and eight subjects trained at the same relative work rates in normoxia (NT; P(I)O(2) 141 mmHg). The training-induced improvement of all the measured parameters were closely matched between the HT and the NT ( P0.05). Training increased T(lim) by 59.7% [164(40) s]. The value of T(lim) was related to VO(2)4%N and to La(max) before and after training. Also, the training-induced improvement of T(lim) was related to the concomitant decrease in La(max). It is concluded that: (1) endurance training including continuous high-intensity exercises improves T(lim) for exercises performed at the same relative (higher absolute) work rate after training, (2) intermittent hypoxic training has no potentiating effect on T(lim) as compared with training in normoxia, and (3) the intra-individual training-induced improvement of T(lim) was associated with metabolic alteration in relation to lactate accumulation.

International audience; The present study was performed to compare various individual muscular efficiency indices, i. e., gross (GE), net (NE), work (WE), and delta (DE), during arm cranking ergometer (ACE) and wheelchair ergometer (WERG) exercise at the same relative exercise intensities. Following a maximal test on both the ACE and WERG, 15 able-bodied subjects completed 4 submaximal bouts at 0, 40, 55 and 70 % of the mode-specific VO(2) peak. The peak power output and VO(2) values were significantly higher with ACE than WERG maximal exercise. As a consequence, the power output imposed during WERG submaximal bouts was significantly lower compared to ACE submaximal bouts. ACE exercise was found to elicit a significantly higher (p < 0.001) VO(2) (16 to 28 vs 14 to 23 ml x min(-1) x kg(-1)), GE (9 to 11 vs 6 to 9 %) and NE (14 to 13 vs 10 to 11 %) compared to WERG exercise at power output from 40 to 70 % VO(2) peak, respectively. However, WE (17 to 15 vs 17 to 14 % at 40 to 55 % VO(2)peak) and DE (12 to 13 vs 12 to 12 % at Delta 40 - 55 % to Delta 55 - 70 % VO(2) peak) values were similar between ACE and WERG exercise. The lower GE and NE observed during WERG compared to ACE exercise could be explained by the biomechanical disadvantages of the hand-rim WERG pattern movement. These findings also supported that the different indices of efficiency influenced the interpretation of the comparison between ACE and WERG propulsion.

The purpose of this study was to evaluate different efficiency indices, i.e., gross (GE: no baseline correction), net (NE: resting metabolism as baseline correction), and work (WE: unloaded exercise as baseline correction), to reveal the effect of endurance training on mechanical efficiency. Nine healthy sedentary women undertook an incremental test and submaximal cycling exercise, at an intensity corresponding to 50% of the pretraining peak oxygen uptake, before and after 6 weeks of endurance training (18 sessions of 45 min). The training effects on efficiency indices were tested by comparisons based on GE, NE, and WE as well as by the differences between the percentage changes of all indices (% GE, % NE, % WE). Endurance training resulted in significantly higher GE (+ 11.1%; p

Background Ankle movements can be partially encoded by cutaneous afferents. However, little is known about the central integration of these cutaneous signals, and whether individual differences exist in this integration. The aim of this study was to determine whether the effect of cutaneous stimulation at the ankle would differ depending on the participants’ preferred sensory strategy appraised by relative proprioceptive weighting (RPw). Methods Forty-seven active young individuals free of lower-limb injury stood on a force platform either barefoot or wearing a custom-designed bootee. Vibrations (60 Hz, 0.5 mm) were applied either to the peroneal tendons or to the lumbar paraspinal muscles. Results The barefoot RPw was strongly negatively correlated to the absolute change in RPw measured in the bootee condition (r = −0.81, P

The present study aimed to investigate the effects of a high-intensity swim test among top-level swimmers on (i) the spatial and temporal parameters of both the stroke and the 3-D fingertip pattern and (ii) the mechanical, muscular, and physiological parameters. Ten male international swimmers performed a 4 × 50 m swim at maximal intensity. Isometric arm flexion force with the elbow at 90° (F90°), EMG signals of right musculus biceps brachii and triceps brachii and blood lactate concentrations were recorded before and after the swim test. Kinematic stroke (stroke length, rate, and velocity) and spatiotemporal parameters of the fingertip trajectory were measured by two underwater cameras during the first and last 50 m swims. After the swim test, F90° and mean power frequencies of the EMG decreased significantly when blood lactate concentration increased significantly, attesting the reaching of fatigue. From the first to the last 50 m, stroke rate, stroke velocity, and temporal parameters of the fingertip trajectory exhibited significant increases although stroke length and spatial fingertip trajectory remained unchanged. General and individual adaptations were observed among the top-level swimmers studied. The present findings could be useful for coaches in evaluating fatigue effects on the technical parameters of swimming.Key words: sport, fatigue, biomechanic, lactate, force.